present invention relates to a valve for containers of aromatic or in any case odorous products, especially particulate or powder products, such as coffee, detergents, organic liquids and the like.
Valves of the above-mentioned type are obviously already known and are commonly called degassing valves. They are one-way valves which are normally applied to the upper wall of the container and whose purpose is to allow the gases developed by the product, for example coffee, to escape from the container, avoiding the possible build-up of internal overpressure, which would cause bulging and/or tearing of the container itself, and at the same time to prevent air from entering the container as this would impair the quality of the product.
The one-way valves used at present serve this purpose perfectly, opening when slight internal overpressures occur and closing immediately when they cease.
However, these valves present great drawbacks due to the following considerations.
Fresh (newly packaged) coffee generates a mixture of gases inside the container, consisting mainly of carbon dioxide and, in a smaller percentage, of so-called aromas, which are characterized by complex molecular chains.
The one-way valves currently in use utilize porous filters, whose sole purpose is to prevent the escape of particles of coffee. In the event of overpressures inside the container, therefore, they allow both carbon dioxide and the product""s aromas to escape, as well as other gases. Valves of this type are described, for example, in Italian patents 823800 and 971505.
Although specific reference is made in this description to coffee, that is to a product with a pleasant aroma, the same problem arises for odorous products in general, such as the detergents and organic liquids mentioned above, for which it would be desirable to avoid the escape of odours, in this case unpleasant ones.
EP-0 659 657 B1 describes a valve of the selective type which allows the gases that form in the package to escape, retaining the product""s aromas. It has been noted, however, that such a type of valve does not allow the complete escape of the oxygen, which tends to oxidize the product with which it comes into contact, detracting from the quality thereof.
It is therefore necessary to close the container after having created a high vacuum by a procedure that tends to slow down the production rates of the packaging machines or else it is necessary to carry out washing with inert gas, again by means of quite a costly procedure.
The package has a slightly bulging appearance according to the overpressure necessary for opening the valve.
The object of the invention is to avoid said drawbacks, and to preserve the nature of the product more or less intact, reducing to a minimum or preventing the escape of aromas or odours, and at the same time ensuring that the oxygen present in the package is eliminated and the carbon dioxide is reduced so that the package does not appear to bulge.
This object is achieved, according to the invention, by providing a degassing valve equipped with a selective filter, which allows the passage of molecules of carbon dioxide and other gases, and traps the molecules that determine the product""s aroma and odours, not allowing them to escape, and which eliminates the residual part of the oxygen, thus enhancing the quality of the product.
Coffee is known to develop a large amount of CO2, equivalent to as much as two or three times its volume, after toasting. Most of this CO2 is eliminated through the valve, whereas the residual amount is absorbed by the filter to such an extent as to further reduce the residual internal pressure inside the package, thereby giving the package a pleasant appearance without bulges.
Porous filters or molecular sieves can be used as selective filters. However, in the tests performed it has been observed that the filters that best perform this selector function are compounds based on activated charcoal, diatomaceous earth, silica, etc, which in any case can be modified by adding additives which make them specific to the individual organic requirements. The oxygen, on the other hand, is adsorbed through oxidoreduction reactions, reactions of addition to organic substances, as already known to the art. The same applies to CO2.
Further characteristics of the invention will be made clearer by the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment thereof, illustrated in the appended drawings, in which: